Electrocardiovectographic device



Nov. 17, 1953 M.'BROSSEL|N ELECTROCARDIOVECTOGRAPHIC DEVICE Filed Aug.2, 1949 Patented Nov. 17, 1953 ELEGTROCARDIOVECTOGRAPHIC DEVICE MichelBrosselin, Courbevoie, France, assignor to Socit dite: Usines Gallus(Societe Anonyme), 'Courbevoie, France, a French corporation ApplicationAugust 2, 1949, Serial No. 108,119

Claims priority, application France August 3, 1948 7 Claims.

The present invention relates to electrocardiographs and particularly toapparatus for producing on the screen of a cathode ray tube an imagecharacteristic of the cardiac vector of a person whose heart is beingexamined.

An electrocardiograph is apparatus for studying the electrical activityof the heart. The heart exhibits electrical activity because themyocardium, i. e. the muscular substance of the heart, carries anegative charge when it is activated and a positive charge when it isresting or has recovered. When both activated and resting mus cle ispresent at the same time in difierent portions of the heart, thedifierence in potential between the two induces an electrical field.This field permeates the body and can be detected by means of electrodeplates on or inside the body. The part of the body that is closer to theresting or recovered muscle is influenced by the positive pole of thefield while that part of the body which is closer to the activatedmuscle is influenced by the negative pole. The electrical field changesfrom instant to instant, both in force and direction, as the activationor recovery proceeds over the heart. The potential picked up byelectrodes in contact with the body changes accordingly. By suitablyplaced electrodes, it is possible to determine both the direction andthe magnitude of the electrical force thus generated in the body.

In order to study the electrical activity of the heart, it is convenientto use a vector which is called the cardiac vector or electrical axis ofthe heart. A vector is a quantitative and graphic representation of aforce, in this case an electrical force. The cardiac vector thusrepresents the electrical force of the heart. Its symbol is an arrow,the length of which is proportional to the magnitude of the force andthe direction of which is the direction of the force. The leading tip ofthe arrow indicates the orientation of the positive pole of theelectrical force. As indicated above, the electrical force iscontinually changing and hence the vector representing it is aninstantaneous vector.

The electrical activity of the heart is acornplicated process which isstill not fully understood. In order to deal with it in a practicalmanher, it is advisable to resort to simplification. For one thing, theelectrical activity may be considered as arising from a single source.Actually, electrical activity is occurring simultaneously in differentparts of the heart but, for the sake of simplification, it may beaveraged up and summated so as to be condensed into a single focus whichis considered as being the center of the heart. This focus is thusconsidered to be the sole origin of the electrical field which permeatesthe body and may hence be considered as the point of origin of a vectorrepresenting the electrical force of that field.

It is an object of the present invention to provide improved apparatusfor producing a visual representation or record of the cardiac vector ofa person whose heart is being examined. By studying the characteristicsof the cardiac vector, doctors are able to determine useful factsconcerning the functioning and condition of the heart.

The objects, advantages and characteristics of the apparatus inaccordance with the invention will be understood more fully from thefollowing description and claims in coniunction with the accompanyingdrawings, in which:

Fig. 1 is a diagrammatic illustration of the manner in which thedirection and magnitude of a cardiac vector are determined.

Fig. 2 is a schematic diagram of apparatus in accordance with theinvention.

Fig. 3 shows a curve obtained with the apparatus.

According to a well established method of elec trocardiography known asthe Einthoven system, three electrodes are secured in contact with thebody of a patient being examined, the electrodes being located at thefollowing points:

1. Right arm, herein designated as R.

2. Left arm, herein designated as L.

3. Left leg, herein designated as F.

For simplicity of calculation, the points at which the three electrodesare located may be considered as the corners of an equilateral trianglewith the heart located at the center of the triangle. The electromotiveforces between the electrodes at any instant may be represented by threecomponent vectors lying on the sides of the equilateral triangle andhence disposed at an angle of to one another. Thus, as illustrated inFig. 1, the electromotive force between points L and R may berepresented by a vector 61, the electromotive force between points R andF may be represented by a vector as and the electromotive force betweenpoints F and L may be represented by a vector es. By vectorially addingthe component vectors e1, c2 and e3, there is obtained a resultantvector This resultant vector represents the cardiac vector or electricalaxis of the heart. In order that the resultant or central vector E maybe taken as originating at the center 0 of the triangle (whichrepresents the center of the heart) the component vectors e1, c2 and 62are plotted on the sides of the triangle starting the respective vectorsand the electromotive forces that these vectors represent.

As will be seen from the foregoing explanation in conjunction with Fig.1, it is possible, theoretically, to take individual readings of thevoltages between respective pairs of the electrodes to ascertain thevalues of the component vectors e1, es and eg and then plot theresultant vector E. However, since the values are constantly changing,graphical determination of the cardiac vector in this manner is notpractical. It is therefore an object of the present inven tion toprovide apparatus which will provide a visual representation of theinstantaneous cardiac vector.

In accordance with the invention, electrometive forces obtained from thebody are amplified and applied to a cathode ray tube or oscillograph insuch manner as to produce an image which is characteristic of thecentral cardiac vector. The apparatus thus obtains the cardiac vectorinstantaneously from the component vectors representing theelectromotive forces between pairs of electrodes. However, when usingthree electrodes, positioned in accordance with the Einthoven system, asdescribed above, the component vectors are not perpendicular to oneanother and can hence not be applied directly to a cathode ray tube oroscilloscope having pairs of deflecting plates disposed at right anglesto one another. It will be understood that a cathode ray tube'of theconventional kind having horizontal and vertical plates operates on theCartesian system of coordinates, the deflection of the cathode beam bythe vertical pair of plates representing the ordinate and the deflectionby the horizontal pair of plates representing the abscissa of thesystem. It is an object of the invention to provide an electrical devicewhich effects the required mathematical correction that is necessary ingoing from a system of oblique component vectors to the Cartesian systemso as to obtain a correct synthesis of the cardiac vector.

As the vector or (Fig. l) is horizontal, the corresponding electromotiveforce can be applied directly (with suitable amplification) to a cathoderay tube to produce proportional horizontal deflection of the cathodebeam. However, the electrornotive forces represented by the vectors ccand c3 cannot be applied directly to the cathode ray tube since they areneither vertical nor horizontal. In order to obtain a correct synthesisof the cardiac vector E, it is necessary to apply a voltage proportionalto the horizontal component e1 to the horizontal deflecting plate of acathode ray tube and to apply to the vertical deflecting plates avoltage proportional to the vertical component of the vector E,represented in Fig. 1 by the line Org. The value of the verticalcomponent of vector E may be determined mathematically, reference beinghad to Fig. 1

O20i=OV and 0157:0102-902 (LOlVO being drawn as 60 and LgOO: being drawnas 30) Ob C2 11 60 sine and tan 30- #5 Therefore:

The Einthoven relation gives us besides:

ez=e1+ca (2) By substituting this value for e: in Equation 1:

Hence, in order to reproduce the cardiac vector E on a cathode ray tube,it is necessary to have a horizontal deflection, i. e. a deflection inthe direction of the X axis. proportional to e1 and avertical'deflection, i. e. a deflection in the direction of the Y axisproportional to l+ 3 #5 Thus, the vectorial synthesis of the cardiacvector E may be obtained solely from the two component vectors e1 and63.

Apparatus for obtaining this synthesis is shown schematically in Fig. 2.Voltages equal or proportional to er and ea are applied either directlyor'after equal amplification to'input terminals, I, l and 2,2,"respectively, of the apparatus, the'terminals I and 2"being connectedtogether and suitably grounded. Thus; input terminals l and l" areconnected; respectively, to the electrodes at points R and L (Fig. 1)while input terminals 2 and 2' are connected, respectively, toelectrodes at points F and L, it being understood that suitablepreamplification may be interposed between the electrodes and the inputterminals. A potentiometer P is connected across the input terminalsland I and a similar potentiometer P1 is'connected across the inputterminals 2 and 2. The sliding contact oi the potentiometer P isapproximately at the middle of the resistance so that the output voltageof the potentiometer is proportional to The sliding contact of thepotentiometer P1 is near the end of the resistance to which the inputterminal 2 is connected so that the output voltage of the potentiometerP1 is proportional to the entire input voltage e3. It will be seen that,if the input voltages er and ea were equal, the output voltage ofpotentiometer P1 would be twice that of the potentiometer P.

The sliding contact of the potentiometer P is connected by conductors 3and 4 to the grids of identical amplifier tubes 5 and 6. The slidingcontact of the potentiometer P1 is connected to the grid of an amplifiertube 1. The cathodes of the amplifier tubes 5, 6 and "I are connectedthrough resistances n, r: and Ta, respectively,

to ground. The plate of amplifier tube 5 is connected through a loadresistance T4 to a high voltage supply indicated at HT, The plates ofamplifler tubes 6 and l are connected to a common terminal 8 and to ahigh voltage supply HT through a common load resistance r5.

Assuming equal amplification by the amplifier tubes 5, s and 1, theoutput voltage of tube 5 will be proportional to while the combinedoutput voltage of tubes 6 and I will be proportional to gi-esMultiplying both quantities by 2', in order to simplify them, the outputvoltage of tube 5 may be considered as being proportional to 61 Whilethe combined output voltage of tubes 5 and 1 may be considered as beingproportional to (Bi-F283.

The common terminal 8 of the plates of tubes 6 and l is connectedthrough a condenser 9 to one end of a potentiometer it which serves as avoltage divider, the opposite end of which is connected by a conductor25 to an acceleration anode it of a cathode ray tube 2!) having a screen25 and. a cathode 22. The sliding contact of the voltage divider it isconnected by a conductor 23 to one of the vertical deflecting plates llof the cathode ray tube 29, The sliding contact of the voltage dividerit! is set so as to divide the voltage (cpl-2e? by the square root of 3,so that the voltage applied to the vertical deflecting plates i of thecathode ray tube is The plate of the amplifier tube 5 is connectedthrough a condenser E2 to one end of a potentiometer E3 the opposite endof which is con nected by conductor is to the acceleration anode it ofthe cathode ray tube 28. The sliding contact of the potentiometer i3 isconnected by conductor 2% to one of the horizontal defleeting plates itof the cathode ray tube. The purpose of the potentiometer I3 is tocompensate for the fact that the horizontal deflecting plates are nearerthe acceleration anode l6 than are the vertical deflecting plates 5 I.It is known that the pair of plates positioned nearest the anodeproduces a greater deflection than the pair of plates farther away fromthe anode if the potentials applied to the plates are equal. In otherwords, the cathode ray tube is more sensitive to the deflection platesnearer the anode. To equalize the sensitivities of the two pairs ofplates, the voltage applied to the plates nearer the anode, i. e. thehorizontal deflecting plates is, is appropriately reduced by thepotentiometer l3.

It will thus be seen that an amplified voltage, proportional to thecomponent vector 61, is applied to the horizontal deflecting plates M ofthe cathode ray tube 2c while an amplified voltage proportional to thefunction is applied to the vertical deflecting plates. The horizontaldeflection of the cathode beam is hence proportional to the vector e1while the vertical deflection is proportional to The resultantdeflection of the cathode beam thus represents in direction andmagnitude the central cardiac vector E.

It is therefore possible, in accordance with the invention, to use acathode ray tube having two pairs of deflecting plates disposed at rightangles to one another and yet produce an image characteristic of thecentral cardiac vector from two component vectors disposed at an angleof less than to one another. As will be seen from the example describedabove, this is achieved by applying to one pair of deflecting plates anamplified voltage proportional to one of said component vectors whileapplying to the other pair of plates an amplified voltage proportionalto the algebraic sum of one of the component vectors and a multiple ofthe other of said component vectors divided by a trigonometric functionof the angle between said component vectors.

In the foregoing description, the central cardiac vector E was obtainedfrom the component vectors c1 and as. It can be obtained in a similarmanner from component vectors c1 and ea or component vectors c2 and es,or from other component vectors disposed at an angle of less than 90 toone another, the potentiometers and other components of the apparatusbeing set in accordance with the mathematical relationship of thecomponent vectors, as illustrated by the example described above.

From the foregoing description, it will be un derstood that theresultant deflection of the cathode beam represents, in direction andamplitude, an instantaneous cardiac vector. The spot made by the cathodebeam on the screen at any instance thus represents the tip of a vectororiginating at the central point 0. The curves C1 and C2 in Fig. 3represent curves traced by the tip of the vector during a cycle in thefunctioning of the heart, To facilitate study of the vector cardiogramthus produced, the cathode ray tube may be rotated about itslongitudinal axis so that the vector E shown in Fig. 3 coincides withthe vertical axis OY.

To avoid blurring of the image on the screen of the cathode ray tube dueto successive images being superposed on one another, the horizontalplates of the cathode ray tube are preferably connected to aconventional sweep circuit (not shown) to impart to the image a sweepingmovement the speed of which is proportional to the frequency of thephenomenon being investigated, e. g. 25 to 75 mm. per second.

By thus applying to the deflecting plates of a cathode ray tube suitablyamplified component voltages obtained from electrodes in contact withthe body, there is obtained an image characteristic of the cardiacvector of a person being examined. By employing a screen capable ofstrong afterglow, the path of the spot produced by the cathode beam onthe screen of the cathode ray tube can still be seen several secondsafter the beam has passed and a visible curve traversing the screen isthus obtained.

I claim:

1. In an electrocardiograph for producing a pattern characteristic ofthe central cardiac vector from two component vectors derived fromelectromotive forces in the body of a person being examined and disposedat an angle of less than ninety degrees to one another, a cathode raytube having two pairs of deflecting plates disposed at right angles toone another, means for obtaining voltages proportional to said componentvectors, means for amplifying one of said voltages and applying it toone of said pairs of plates, means for amplifying the other of saidvoltages, circuit means for algebraically adding one of said amplifiedvoltages and a multiple of the other, and circuit means for dividingsaid sum by a trigonometric function of said angle and applying saiddivided voltage to the other of said pairs of plates.

2. In an electrocardiograph for producing a pattern characteristic .ofthe central cardiac vector from two component vectors, er and es,derived from electromotive forces in the body of a person being examinedand disposed at an angle of approximately sixty degrees to one another,a cathode ray tube having two pairs of deflecting plates disposed atright angles to one another, means including an amplifier for applyingto one of said pairs of plates a voltage proportional to the vector 21,means including an amplifier for providing a voltage proportional to twotimes the vector as, circuit means for adding the voltage proportionalto the vector 61 and the voltage proportional to two times the vector63, and circuit means for dividing the sum of said last mentionedvoltages by the square root of three and applying the resulting voltageto the other of said pairs of plates.

3. In an electrocardiograph for producing an image characteristic of thecentral cardiac vector from two component vectors derived fromelectromotive forces in the body of a person being examined and disposedat an angle of less than ninety degrees to one another, a cathode raytube having a screen, means for producing a cathode ray and two pairs ofdeflecting plates disposed at right angles to one another, meansincluding an amplifier for applying to one of said pairs of plates avoltage proportional to one of said component vectors, means includingan amplifier for providing a voltage proportional to a multiple of theother of said component vectors, circuit means for adding said twovoltages, and circuit means for dividing the sum of said two voltages bya trigonometric function of the angle between said component vectors andapplying the resulting divided voltage to the other of said pairs ofplates, the voltages applied to said plates acting to deflect thecathode ray to produce said image on said screen.

4. In an electrocardiograph for producing an image characteristic of thecentral cardiac vector from two component vectors derived fromelectromotive forces in the body of a person being examined and disposedat an angle of less than ninety degrees to one another, a cathode raytube having a screen, means for producing a cathode ray and two pairs ofdeflecting plates disposed at right angles to one another, means forequalizing the sensitivity of the two pairs of plates, means includingan amplifier for applying a voltage proportional to one of saidcomponent vectors to one of said pairs of plates, means including anamplifier for providing a voltage proportional to a multiple of theother of said component vectors, circuit means for adding said twovoltages, circuit means for dividing the sum of said two voltages by atrigonometric function of the angle between said component vectors andmeans for applying the resulting voltage to the other of said pairs ofplates.

5. In an electrocardiograph for producing an image characteristic of thecentral cardiac vector from two component vectors derived fromelectromotive forces in the body of a person being examined and disposedat an angle of less than ninety degrees to one another, a cathode raytube having a screen, means for producing a cathode ray and two pairs ofparallel deflecting plates, the plates of one pair being in planesperpendicular to the planes of the plates of the other pair, means forobtaining voltages proportional to each of said component vectors, meansfor amplifying one of said voltages, means for applying said amplifiedvoltage to one of said pairs of plates, means including an amplifier forobtaining a voltage proportional to a multiple of the other of saidvoltages, circuit means for adding to the voltage thus obtained avoltage equal to the first mentioned amplified voltage, circuit meansfor dividing the sum of said last mentioned voltages by a trigonometricfunction of the angle between said component vectors and means forapplying the resulting divided voltage to the other of said pairs ofplates.

6. In an electrocardiograph for producing an image characteristic of thecentral cardiac vector from two component vectors derived fromelectromotive forces in the body of a person being examined and disposedat an angle of less than ninety degrees to one another, a cathode raytube having a screen, means for producing a cathode ray and two pairs ofparallel deflecting plates, the plates of one pair being disposed atright angles to the plates of the other pair, terminals for receiving afirst voltage proportional to one of said component vectors, a voltagedivider connected across said terminals, first and second amplifiersconnected in parallel to the output or" said divider, means including avariable voltage divider for applying the output of said first amplifierto one of said pairs of plates, terminals for receiving a second voltageproportional to the other of said component vectors, a voltage d viderconnected across said last mentioned terminals, a third amplifierconnected to the output of said last mentioned divider, means connectingthe outputs of the second and third amplifiers to a common terminal andmeans including a variable voltage divider connecting said commonterminal with the other of said pairs of plates.

7. In an electrocardiograph for producing an image characteristic of thecentral cardiac vector from two component vectors derived fromelectromotive forces in the body of a person be ing examined anddisposed at an angle of less than ninety degrees from one another, acathode ray tube having two pairs of deflecting plates disposed at rightangles to one another, means for providing a first voltage proportionalto one of said component vectors, means for amplifying said voltageincluding first and second amplifiers connected in parallel with oneanother, means for applying the output of said first amplifier to one ofsaid pairs of plates, means for providing a second voltage proportionalto the other of said component vectors, a third amplifier for amplifyingsaid second voltage, means connecting the outputs of the second andthird amplifiers to a common terminal and means including a variablevoltage divider connecting said common terminal with the other of saidpairs of FOREIGN PATENTS plates. Number Country Date MICHEL BROSSELIN-424,162 Great Britain Feb. 15, 1935 OTHER REFERENCES A method ofanalyzing the electrocardiogram, by Hubert Mann, volume 25, N0. 3, of Nher Name Date the ATOhIVSS of Internal Medicine, pages 282 to 2 HellerSept 10 1940 294, inclusive, of the issue of March 1920. A 2:229698Honmann Jan 23 1941 10 copy of this work is available in Division 55 ofthe 2 2 4 15 s et 1 A 25 1942 United States Patent Office.

References Cited in the file of this patent 5 UNITED STATES PATENTS

